What? The perk descriptions for New Vegas and Fallout 3 are the exact same for both Lady Killer and Black Widow. And they function exactly the same.

"In combat, you do +10% damage against [female/male opponents]. Outside of combat, you'll sometimes have access to unique dialogue options when dealing with the opposite six."

The "unique dialogue options part is the seduction/sixuality aspect. Of which you can use it multiple times. Although not as much as in New Vegas, its significantly more useful in that game. Nova, The Antagonizer, and a few others can all be "seduced" with it.

Edit: Here's the full list of women affected by Lady Killer in F3:

• http://fallout.wikia.com/wiki/Nova in http://fallout.wikia.com/wiki/Megaton will provide the player character with the password tohttp://fallout.wikia.com/wiki/Colin_Moriarty's terminal.
• http://fallout.wikia.com/wiki/Brianna in the http://fallout.wikia.com/wiki/Blood_Ties quest will provide the player character with the password to http://fallout.wikia.com/wiki/Ian_West's cell.
• One can talk the http://fallout.wikia.com/wiki/AntAgonizer into stopping her attacks on the town and ending her feud with http://fallout.wikia.com/wiki/Scott_Wollinski. The Lone Wanderer also gets her costume.
• One can talk http://fallout.wikia.com/wiki/Fantasia into stealing http://fallout.wikia.com/wiki/Dukov's key for the quest http://fallout.wikia.com/wiki/You_Gotta_Shoot_%27Em_in_the_Head. It is possible to do this without the perk though, but Lady Killer eliminates the possibility of a http://fallout.wikia.com/wiki/Speech check failure.
• One can talk http://fallout.wikia.com/wiki/Agatha_Egglebrecht into giving them the key to her ammunition box to help the Lone Wanderer during the questhttp://fallout.wikia.com/wiki/Agatha%27s_Song.
• In http://fallout.wikia.com/wiki/Operation:_Anchorage_(add-on), one can calm http://fallout.wikia.com/wiki/Olin down and get more detailed information on questions. Also, the conversation will not end after each question.
• One can talk http://fallout.wikia.com/wiki/Ronald_Laren in the http://fallout.wikia.com/wiki/Nuka-Cola_Challenge quest into a threesome. He then runs to the factory himself. He always ends up dead just inside the factory door if the player character does this.

And the full list of men affected by Black Widow in F3:

• One can talk http://fallout.wikia.com/wiki/Burke_(Fallout_3) in http://fallout.wikia.com/wiki/Megaton into paying double http://fallout.wikia.com/wiki/The_Power_of_the_Atom, or giving up on the bomb entirely.
• One can talk http://fallout.wikia.com/wiki/Karl_(Fallout_3) into giving up the password to http://fallout.wikia.com/wiki/Ian_West's room during the http://fallout.wikia.com/wiki/Blood_Ties quest.
• One can talk http://fallout.wikia.com/wiki/Scott_Wollinski into ending the battle with his nemesis, the http://fallout.wikia.com/wiki/AntAgonizer. The Lone Wanderer also gets his costume.
• One can talk http://fallout.wikia.com/wiki/Dukov out of his key without paying for it during the quest http://fallout.wikia.com/wiki/You_Gotta_Shoot_%27Em_in_the_Head.
• One can convince http://fallout.wikia.com/wiki/Ramsey into selling slaves to the player character during the quest http://fallout.wikia.com/wiki/Into_The_Pitt.
• One can talk with http://fallout.wikia.com/wiki/Morrill at the beginning of http://fallout.wikia.com/wiki/Operation_Anchorage, so the Lone Wanderer can come through after the elevator, but that should not be a problem even if they don't have the Black Widow perk.
• One can convince http://fallout.wikia.com/wiki/Wernher to give you 120 http://fallout.wikia.com/wiki/5.56mm_round_(Fallout_3), should one decide to side with the slaves in the questhttp://fallout.wikia.com/wiki/Free_Labor.
• One can use this perk on http://fallout.wikia.com/wiki/Sibley in the beginning of the Operation: Anchorage quest-line, where he will lead the player character to Protecter McGraw without the aggression. He still turns on the player character at the end, though.
• One can use this perk on http://fallout.wikia.com/wiki/Paulson when he is first encountered onboard http://fallout.wikia.com/wiki/Zeta. He will tell the Lone Wanderer why he wants revenge.

And yes, New Vegas is canon. Its developed by Obsidian, but is published by Bethesda Softworks. Its in the same realm as Fallout 3 with regards to canon: canon unless Bethesda for some strange reason decides to make it not so.

You state in your post the there is only one orientation in FO3 straight and then claim that there is a gender gate to Lady killer and Black widow.

So there is no actual sixuality tied to the two perks by Bethesda because sixuality isn't variable in FO3. That is like saying Vault boy perk which is different from vault girl, they have separate id codes are heterosixual because you can only be heterosixual in FO3 and you can't take Vault girl as a male. That is a logical fallacy. Just because there is a gender gate on a perk and the only sixuality is Hetrosixual doesn't actually mean all gender gated perks are tied to sixuality.

And obsidian's actions do not in any way tie Bethesda to anything. The features they added to NV do not beholden Bethesda in anyway to emulate. So who the frak cares what a third party did? What is important is what Bethesda did in the past and how it will shape the future.

We already know that sixual orientation is in the game, we already know that companions can be wooed regardless of the protagonist's gender so why do we need perks to unlock same six content?

How is this tied to sixuality? Have you never met charismatic flirts that can flirt with either gender? I have met more than a few woman that are gay that can flirt with men, and I know more than a few gay men can flirt/manipulate women. Again where is the sixuality attached to the perk? I worked at a restaurant in college and knew more than a few waiters that flirted with gay customers for better tips who were straight and you have probably met a lisbian waitress that flirted with men even if you didn't know it. I am not seeing how a perk that is designed to make you better at killing a gender and manipulating them means you automatically fancy them in the sack and locks you sixuality in place because you took said perk.

Some gamers have really scary views on sixuality. But it would explain why there is such hate for female gamers. They may want to sleep with female gamers but they all took the lady killer perk so they want to be better at harming them too?

First of all real life =/= game mechanics. This has nothing to do with the real life complexities of gender and sixuality. Its a perk, in a freaking video game. These are its stated mechanics. Its designed to be a perk which allows characters unique dialogue based on their ability to "seduce" the opposite six. In New Vegas, non-hetero perks are added which function similarly for players who wish their gay or lisbian characters to be schmoozers. There is no perk for a bi-sixual character, just like there is no perk for a a number of real-life character traits.

However, clearly the intent is that the player is a "Lady Killer"/"Black Widow" which in slang terms is:

Lady Killer: a charming man who is very attractive to women.

Black Widow: A disingenuous woman who exploits her position in a relationship to the detriment of her partner.

The intent of course being that you're using your characters sixuality to manipulate the individual. Absolutely your character could be gay, if you'd prefer, and still take the Lady Killer perk. However, even then there is still no denying that the gay character is using the allure of six and a faux "straight" sixuality to manipulate women. Even if he has absolutely no intent of actually following through. So even in that situation, there's still sixuality inherently tied to the perk.

The fact that your character does damage to the opposite six is entirely a play on words. In essence your character becomes a "figurative" Lady Killer and Black Widow along with a "literal" one. Its basically just a joke and a little extra something meant to give value to the perk gameplay-wise. That's all.

I agree!!